Whitening agent composition and process for its manufacture



v, RISE.

Patented Mar. 13, 1962 3,025,242 ENHNG AGENT COMPOfilTlON AND PRQQIESS FOR ll'lfi MANUFACTURE Ralph Crawford Seyler, Wilmington, De.l., assignor to E. 1. tin Pont de Nemours and Company, Wilmington,

DelL, a corporation of Delaware No Drawing. Filed Mar. 20, 1961, Ser. No. 96,713

6 Claims. (Cl. 252-301.3)

This invention relates to whitening compositions for use in whitening textile fibers and paper. It is an object of this invention to provide a composition of matter for the aforementioned purpose which is in the form of a concentrated aqueous solution, adapted to be diluted to the desired concentration of the treatment bath with minimum mechanical effort, and which will exert a whitening effect equal to the best effects obtainable hitherto from the same whitening agents in other physical forms or modes of ap plication. Another object is to provide a process for preparing said dilutable composition directly from available intermediates with a minimum of handling, and avoiding in particular isolations of intermediate products, removal of by-product salts and similar time consuming and energy wasting operations. Various additional objects and achievements of this invention will become apparent as the description proceeds.

The use of fluorescent agents for whitening textile fibers and paper is per se well known. A class of agents commonly used for this purpose are the bis-triazinyl diaminostilbene derivatives set forth in US. Alien Property Custodian specification Serial No. 381,856, published May 11, 1943, and one particularly popular member of this class is the dianilino bis-diethanolamino bis-triazine compound set forth in Example 16 of said A.P.C. specification.

Now, although the above dianilino compound has excellent aifinity and exhibits a strong build-up when applied to textiles or paper in relatively large amounts, it becomes unevenly distributed on the substrate and presents an un level fluorescent whitening effect, when applied in small amounts. A more level dyeing whitening agent has lfreen needed. Besides, the anilino compound is effectivze as a whitening agent only at a pH above 6.0; belorw this value the compound precipitates and is lost to Such an acidic pH often exists in a paper machine size-bath containing the whitening agent due to the presence of alum accumulated in the bath from the paper sheet passing continuously through the machine. Furthermore, in manufacturing a marketable aqueous concentrate of the said anilino compound, it has been found essential that the bulk of the by-product sodium chloride formed in the synethesis of said compound be removed, so that the concentration of sodium chloride in the marketable concentrate Should not be over one per cent by weight. To obtain a marketable solution having this low salt concentration, the whitening agent must be precipitated either by salting or by converting it to the free acid, separated by filtration, washed to remove the sodium chloride present, and then dissolved in a solution of water and a selected co-solvent with or without an alkaline agent as required to attain solution. Such a procedure consumes time and labor, requires extra equipment, and is to be avoided in the interest of economy.

According to my present invention, the aforenoted difficulties and labors are overcome, and an easily dilutable, marketable aqueous concentrate of a potent whitening agent is obtained, firstly by selecting as active ingredient a compound of essentially the same general formula as above except that the two terminal aniline radicals are replaced by radicals of sulfanilic acid. I find that the whitening agent thus obtained is so much more soluble in water than the corresponding dianilino compound that it is no longer necessary to separate therefrom the sodium chloride formed in its synthesis.

Furthermore, the said whitening agent, which to my knowledge is a new compound, can be readily formulated into a stable, marketable aqueous concentrate by admixing therewith a certain proportion, as specified below, of a co-solvent selected from the group consisting of (a) alkanolamines of the formula (HO-alk) NR wherein alk is a bivalent alkane radical of 2 to 4 carbon atoms, R is hydrogen or alkyl of l to 2 carbon atoms, and x is an integer from 1 to 3, and (b) a polyethylene glycol of the formula H(OCH CH ,OH, wherein n is an integer from 4 to 6.

Finally, my novel choice of the fluorescent compound enables me to carry out the synthesis thereof and formation into a marketable concentrate in one continuous op eration, without isolating any intermediate products or by-products and with a minimum handling of materials in general.

The process of synthesis and compounding into a man ketable concentrate, according to this invention, is in general terms as follows:

Stoichiometric quantities of the requisite initial materials are reacted in a sequence of three condensation steps in an aqueous acetone medium to form the said fluorescent whitening compound; then a co-solvent as above mentioned is added, and a portion of the water is distilled off to form a marketable aqueous concentrate.

In the first condensation step (which follows well known procedure), one mole of 4,4-diamino-2,2'-stilbenedisulfonic acid, neutralized with sodium carbonate or hydroxide, is reacted at a temperature not exceeding 5 C. with 2 moles of cyanuric chloride (which has been dispersed in water from an acetone solution) to form 4,4-bis(4,6- dichloro-s-triazin-Z-ylamino)-2,2 stilbenedisulfonic acid, disodium salt. The I-lCl which is formed in the reaction is neutralized with a base, such as caustic soda or soda ash, maintaining the pH preferably at 3 to 4. When this reaction is complete, as shown by a diazotization test for the presence of any unreacted diaminostilbenedisulfonic acid, 2 moles of sulfonilic acid sodium salt are condensed at 5 to 40 C. with the product of the first reaction to form 4,4'-bis[4-chloro-6-(p-sulfoanilino)-s-triazin- 2-ylamino]-2,2'-stilbenedisulfonic acid, tetrasodium salt. The HCl formed in this reaction is neutralized with a base, maintaining the pH at preferably 4 to 6. The completeness of this reaction is likewise determined by testing 7 for the presence of residual sulfanilic acid by diazotization. Finally, without altering the reaction medium, 2 moles of diethanolamine are condensed in the presence of soda ash, at a temperature above 70 C. and pH of 8 to 9, with the product of the first two steps of the reaction to form the final product, 4,4-bis[4-diethanolamino 6 (p sulfoanilino) s triazin 2 ylamino]- 2,2-stilbene-disulfonic acid, tetrasodium salt.

Optionally, 4 moles of diethanolamine may be used as the reactant in the final reaction, the soda ash being omitted; two moles will condense as stated above, the two moles will neutralize the 2 moles of hydrochloric acid which are formed during the condensation. Thus, in place of forming sodium chloride, diethanolammonium chloride will be formed, and the salt content of the solution will comprise a mixture of 4 moles of sodium chloride and 2 moles of diethanolammonium chloride, rather than 6 moles of sodium chloride, for each two moles of initial cyanuric chloride. When this optional procedure in the third condensation step is followed, the resultant fluorescent whitening agent possesses a pinker shade, which gives a Warmer white and is often more desirable than the greenor blue-white shade that is produced in the absence of said diethanolammonium chloride.

The third condensation step above is generally efiected at a temperature between 70 and C., and preferably at 80 to 95 C. Acetone, which was used in the dispersion of the cyanuric chloride, distills off during this step.

When said third condensation is complete, the reaction mass comprises the whitening agent product as active ingredient, sodium chloride, and possibly in the optional case diethanolammonium chloride, and water. To this mixture is now added an alkanolamine or a polyethylene the temperature of the reaction mass is raised to 40 C. and held at this temperature until a diazotization test shows that condensation is complete. 73 parts of diethanolamine are now added, and the temperature of the reaction mass is raised to 95 C., while allowing the acetone to distill from the reaction mass. After holding the reaction mass at 95 C. for 3 hours, the reaction is complete and contains in solution a compound of the formula glycol, to act a co-solvent with the water, to give a stable solution of the whitening agent in the presence of the by-product chloride salts.

Typical illustrations of the alkanolamines usable as co-solvent are: the mono-, diand triethanolamines; mono-, diand tributanolamines derived from l-butanol, 2-butanol, or l-methyl-Z-propanol; N-methyldiethanolamine; N,N-dimethylethanolamine; and N,N-diethylethanolamine. The preferred compound is triethanolamine.

Preferred members of the polyethylene glycols for use as co-solvent are those which have from 4 to 6 ethylenoxy units per molecule (i.e. a molecular weight roughly of about 200 to 300).

The preferred concentration of the active ingredient (fluorescent whitening agent) in the ultimate, marketable concentrate is from 10 to 30% by weight. The quantity of co-solvent should be not less than 0.5 times the weight of the active ingredient in the concentrate. Accordingly, it can vary from 5 to 30% by weight of the entire concentrate. The quantity of salt, of course, is incidental and will normally be equal to that formed as by-product in the reaction. Accordingly, it will generally add up to about 6 moles total inert salts per mole of the fluorescent whitening agent in the concentrate, said 6 moles comprising from 4 to 6 moles of sodium chloride and the remainder (if any) being diethanolammonium chloride.

It is remarkable that if an isomeric fluorescent agent derived from metanilic acid (in lieu of sulfanilic) is selected, stable aqueous concentrates of the above activeingredient concentration are not obtainable (even when the mentioned co-solvents are employed), because of the strong tendency of the isomeric fluorescent compound to be salted out of solution by the action of said by-product quantities of NaCl.

Without limiting this invention, the following examples are given to illustrate my preferred mode of operation. Parts mentioned are by weight.

Example 1 A solution containing 50 parts of cyanuric chloride in 260 parts of acetone is mixed with agitation with 650 parts of ice and 150 parts of water. To the resultant dispersion are added slowly 350 parts of a water solution containing 50 parts of 4,4'-diamino-2,2-stilbenedisulfonic acid previously neutralized with sodium hydroxide. At the same time a solution of soda ash is also fed in to maintain moderate blue coloration on Congo red test paper. The temperature of reaction is not permitted to exceed 5 C. The condensation is tested for completeness by diazotizing a sample of the reaction mass and testing for color formation with R salt.

To the reaction mass are now slowly added 46.7 parts of sulfanilic acid sodium salt and a 15% soda ash solution, to neutralize the liberated hydrochloric acid and maintain a pH of about 4 to 6. During this addition,

which may be named 4,4'-bis[4-diethanolamino-6-(p-sulfoanilino) s triazin 2 ylamino] 2,2 stilbenedisulfonic acid, tetrasodium salt.

To the above solution are now added parts of triethanolamine, and the solution is concentrated by distillation, to leave a total of 890 parts of a stable, marketable concentrate, which contains, by Weight, 17.7% whitening agent, 10.1% triethanolamine, 1.8% diethanolamine (excess reactant), 3.5% sodium chloride, 4.3% diethanolammonium chloride, and 62.6% water.

When the above concentrate is diluted with water at room temperature to a concentration of 0.1% by Weight of the whitening agent and white, sized paper is dipped into the solution, squeezed, and dried at 65 C., the paper is found to be uniformly white and bright and acceptable for commercial use. Moreover, if the diluted treatment bath is made acid to a pH of 4.0, no visible change therein occurs; the solution remains clear and free from any precipitated material and still provides a brilliant whitening effect on paper.

Example 2 By the procedure of Example 1, 35 parts of cyanuric chloride, dissolved in 180 parts of acetone and mixed with 450 parts of ice and 105 parts of water, are reacted with 35 parts of 4,4'-diamino-2,2-stilbenedisulfonic "acid previously neutralized with sodium hydroxide. The at termediate product is then condensed with 32.7 parts of sulfanilic acid sodium salt, and this product in turn is heated with 102 parts of diethanolamine, with the simultaneous removal of the acetone. This quantity of diethanolamine is enough to leave 62 parts thereof to serve as co-solvent after the condensation is complete. The final composition (which now has a mass of over 1000 parts due to the addition of 15% aqueous soda ash during the first two condensation steps) is concentrated by distilling off a portion of the water, to give a total of 1000 parts of an aqueous concentrate containing 11% of the whitening agent (of the same formula as in Example 1), 6.2% of diethanolamine, 2.2% of sodium chloride, 2.7% of diethanolamonnium chloride, and 77.9% of water.

When a portion of the above solution is diluted to a concentration of 0.05%, acidified to a pH of 4.5, and applied to paper as in Example 1, a uniform, brilliant whitening effect is obtained. No precipitation of the whitening agent occurs.

Example 3 By the procedure of Example 1, parts of cyanuric chloride, dissolved in 500 parts of acetone and mixed with 1235 parts of ice and 285 parts of water, are reacted with 95 parts of 4,4-diamino-2,2-stilbenedisulfonic acid previously neutralized with sodium hydroxide. The in termediate condensation product is then condensed with 89 parts of sulfanilic acid sodium salt, and this product in turn is condensed with 108 parts of diethanolamine, with 3,025,242 '5 6 the simultaneous removal of acetone. To the reaction Paper treated with the above solution, diluted to a conmass are th n added 300 p r f p lv y gly centration of 0.08% of the whitening agent, exhibits an ing (Predominantly) the formula z z)4 and even distribution of the agent, absence of spottiness, and

this final composition is concentrated by distilling oil water a brilliant fluorescent Whitening to glve a total of 1000 Parts of a l homogeneous 5 The final liquid concentrate in each of the above examaqueous concentrate. The latter contalns, by weight, 30% P165 is a clear, light yenow or ambepcolored solution,

of the whitening agent of Example 1, 30% of the above o p y y g y 60% of Sodium chloride 7.3% of which 18 stable to storage over the ran e ot temperatures diethanolammonium chloride and 26.7% of Water. normally encountered m Warehouses m summer and ter On dilution of the above concentrate to 0.1% of con- 1 Wm centration of whitening agent and application of the dilute It W111 be understcfod h of above exsolution to paper, a brilliant, level whitening effect is amples l vaned wldely Wlthm S k1n of obtained engaged in this art. For instance, the initial cyanuric Example 4 chloride may be reacted first with the sodium sulfanilate and then with the disodium salt of 4,4-diarnino-2,2-

A by h Prqcedme 9 Example 86 Parts of stilbenedisulfonic acid, the temperature and pH condicltanuncfihlmdet dlssolvaid m 450 parts of acetone and tions of the two successive condensations being neverthe mlxed Wm} 1115 parts of Ice i q parts, are less the same, respectively, as in the first and second conreatfted .wlth part s 0f & dlarpmo'2.z 'smbenedliul' densation steps in the procedures above set forth. Other fonic acid previously neutrallzed with sodium hydroxide. f0 .11 b ar t The intermediate condensation product is then condensed penmisl vanal Us W1 6 Y, app en with 80 parts of sulfanilic acid, and this product in turn Whlle the examples 3 Llustmted h use of is condensed with 49 parts of diethanolamine with the my novel g enmg composition on paper, it may be simultaneous feeding in of a 15% solution of soda ash to applied also in Similar manner to textile fibers for maintain a pH between'8 and 9. The acetone distills off Stance Fotton f as the temperatureis raised to effect the diethanolamine I clalm Y fnventlon: condensation. To the reaction mass are then added 150 A readlly dllutable Composltlon use as a brightparts ofrnonoethanolarnine, and this composition is conni g agent for cotton fibers p p comprising an centrated by distilling oil water to give 1000 parts of a aqueous concentrate of a fluorescent whitening agent of clear concentrate containing 27% of the Whitening agent, 30 the formula S OgNB. S OgNB HN(]% (IJNH CH=OH NH(| (lf-NH N N N N O Na 031N3- t t N(CH2CH2OH): N(CH2CH2OH) 15% got monoethanolamine, 8.1% of sodium chloride, and and of a co-solvent selected from the group consisting 49.9% of water. of (a) alkanolamines of the formula (HO-alk) -NR Thiis concentrate, when diluted to a concentration of wherein alk is a bivalent alkane radical of 2 to 4 carbon !b.i)5% of whitening agent and applied to paper as in atoms, R is a member selected from the group consisting Example 1, provides a paper with a high level of whiteof hydrogen and alkyl of 1 to 2 carbon atoms, and x is ness and brightness. an integer from 1 to 3 and (b) a polyethylene glycol of Example 5 the formula I-I(OCH CH Ol-I, wherein n is an integer By the procedure of Example 4, 32 parts of cyanuric from 4 to 6, the quantity of said fluorescent whitening chloride, dissolved in 180 parts of acetone and mixed with bemg from 10 to by Welght of the enlflre 400 parts of ice and 100 parts of water, are reacted with posmon and the quantity of Sald co'solvent being suffi 32 parts of 4,4'-diamino-2,2-stilbenedisulfonic acid pre- Giant maintain szfid E -F of Whitening viousiy neutralized with sodium hydroxide. Then in turn agent 111 Stable l f 11 id composi ion. the reaction mass is reacted with 30 parts of sulfanilic The composltlon clalm comammg further mart acid and 18 parts of diethanolamine, employing soda ash Salts from gr p which are formed as i -P in to neutralize the byproduct hydrochloric acid as it is synthesls of Said fluorescent Whitening agent, but in formed. To the reaction mass are then added 300 parts q y not exceeding that which is formed in said y of tri(2-propanol)amine, and the mass is concentrated thesis.

by distillation to give a total of 1000 parts of a clear solu- 3. A readily dilutable composition for use as a brighttion containing 10% of the whitening agent, 30% of ening agent for cotton fibers and paper, comprising an tri(2-propanol)amine, 3.0% of sodium chloride, and aqueous concentrate of a fluorescent whitening agent of 57% of water. the formula 8 OgNil S OgNS.

HNC c-NH CH=OH NFL-(l3 (ll-NH N N N N some some;

a co-solvent selected from the group consisting of (a) alkanolamines of the formula (HO-alk) NR wherein alk is a bivalent alkane radical of 2 to 4 carbon atoms, R is a member selected from the group consisting of hydrogen and alkyl of 1 to 2 carbon atoms, and x is an integer from 1 to 3 and (b) a polyethylene glycol of the formula H(OCH CH ),,OH, wherein n is an integer from 4 to 6, and inert salts selected from the group consisting of sodium chloride and diethanolammonium chloride, said fluorescent agent being present in quantity of to 30% by weight of the entire composition, said cosolvent being present in quantity of 5 to 30% by weight, and said salts being present in a quantity not exceeding 6 moles of total salts per mole of fluorescent whitening agent present in said composition.

4. The composition of claim 3, wherein said co-solvent is triethanolamine.

5. The process of producing a readily dilutable composition adapted for use as a brightening agent for cotton fibers and paper, which comprises condensing, in aqueous acetone medium, essentially two moles of cyanuric chloride with one mole of 4,4'-diamin0-2,2-stilbenedi(sodium sulfonate), condensing the intermediate product thus obtained with two moles of sodium sulfanilate, further condensing the reaction mass with two moles of diethanolamine, adding to the reaction mass a co-solvent selected from the group consisting of (a) alkanolamines of the formula (HO-alk) NR wherein alk is a bivalent alkane radical of 2 to 4 carbon atoms, R is a member selected from the group consisting of hydrogen and alkyl of 1 to 2 carbon atoms, and x is an integer from 1 to 3,

8 and (b) a polyethylene glycol of the formula H(OCH CH ),,OH, wherein n is an integer from 4 to 6, and heating the resulting mixture to drive oft water and acetone until an aqueous concentrate containing, by weight, from 10 to 30% of said triple condensation product is obtained.

6. A process as in claim 5, wherein each condensation step is efiected in the presence of an acid binding agent, the binding agent in the first two steps being a member of the group consisting of sodium hydroxide and sodium carbonate and the binding agent in the third condensation step being a member of the group consisting of sodium hydroxide, sodium carbonate and an excess of the diethanolamine employed in said third condensation step.

References Cited in the file of this patent UNITED STATES PATENTS 2,171,427 Leipzig et al. Aug. 29, 1939 2,595,030 Wallace Apr. 29, 1952 2,763,650 Ackermann Sept. 18, 1956 2,878,248 Crounse Mar. 17, 1959 FOREIGN PATENTS 647,718 Great Britain Dec. 20, 1950 128,651 Australia Mar. 16, 1945 OTHER REFERENCES Ser. No. 381,856, Wendt (A.P.C.), published May 11, 1943.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,025,242 March 13, 1962 Ralph Crawford Seyler It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l line 21, for "isolations" read isolation column 2 iine 56 for "the" read and --3 column 3, line 2O, for "a'fl first occurrence read as ---3 columns 3 and 4,,

lines 8 to 20, and columns 5 and 6 lines 31 to 43 for the lower right-hand portion of the formulas reading "N(CH CH OH) each occurrence read N(CH CH 0H)2 Signed and sealed this 26th day of June 1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

3. A READILY DILUTABLE COMPOSITION FOR USE AS A BRIGHTENING AGENT FOR COTTON FIBERS AND PAPER, COMPRISING AN AQUEOUS CONCENTRATE OF A FLUORESCENT WHITENING AGENT OF THE FORMULA 